Hydrogen is the element with atomic number 1. It is represented by the symbol H. Hydrogen has an average atomic weight of 1.00794 (1.007825 for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's elemental mass Stars in the main sequence are mainly composed of hydrogen in its plasma state. Naturally occurring elemental hydrogen is relatively rare on Earth.
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Hydrogen is the element with atomic number 1. It is represented by the symbol H. Hydrogen has an average atomic weight of 1.00794 (1.007825 for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's elemental mass Stars in the main sequence are mainly composed of hydrogen in its plasma state. Naturally occurring elemental hydrogen is relatively rare on Earth.